1. Field of the Invention
The present invention generally relates to a bonded structure using conductive adhesives, and a manufacturing method thereof, and especially relates to solder-free mounting of electronic parts, particularly electronic parts mounting using conductive adhesives, and a method thereof.
2. Description of the Related Art
In electronic device mounting, a bonding technology using conductive adhesives is drawing attention, since the bonding technology can be used at a temperature lower than required by soldering. Further, since the conductive adhesives provide a higher stress relief function than soldering, it is expected that resilience against thermal distortion will be high. Nevertheless, since the conductive adhesives provide lower bonding strength, there is a problem that damage, such as boundary exfoliation, occurs.
A solution has been proposed for bonding two electric structures, each having an electrode. The proposed solution provides an electrode bonding section A that is bonded to the electrode of one of the two electric structures, another electrode bonding section A that is bonded to the electrode of the other electric structure, and a middle section B that is provided between the two electrode bonding sections A, wherein each section A is made to be “hard bonded”, and the section B is made to be “soft bonded” in order to improve the bonding strength.
According to a technology disclosed by JPA 2002-271005, the “hard bonding” of the section A is realized by “alloying” (fusing) the electrode and conductive filler pieces, and the “soft bonding” of the section B is realized by employing “conductive adhesives containing conductive particles (conductive filler pieces)”. However, for “alloying” (fusing) the conductive filler pieces (conductive particles) having an oxidized film, a special process that includes ultrasonic vibration, pressurization, and heating is necessary. Since a high temperature is used in the heating process, there is a problem that the electric structures to be bonded, such as an electronic device and a substrate, are damaged.
[Patent Reference 1]
JPA 2002-271005